The aims of this project are: (1)\to study the structure-function relationships in the alphafetoprotein (AFP) molecule, making use of the proteolytic fragments and monoclonal antibodies reactive with various parts of the AFP molecule; (2)\to use the monoclonal antibodies reactive with carbohydrate-bearing fragments of AFP in the development of assays specific for the concanavalin A molecular variants of human AFP; (3)\to study the usefulness of monoclonal antibodies in immunolocalization of AFP-producing tumors. During the past year, we have explored the role of monoclonal AFP antibodies in tumor diagnosis and experimental therapy at two levels. The use of monoclonal anti-AFP in radioimmunolocalization of AFP-producing tumors has been studied in collaboration with Dr. David Goldenberg at the University of Kentucky. We have produced several grams of monoclonal antibody for this study, the first results of which look promising. The monoclonal antibody has given a better localization of the antibody to tumors than goat antibody. In a parallel in vitro study, we have been developing a tumor model, using an AFP-producing hepatoma cell line to study the effect of monoclonal antibody-ricin A chain conjugates on these cells. The work on the effects of cytotoxic anti-AFP conjugates in vitro will be continued and expanded to tumor localization studies in nude mice. The transfer of fatty acids by AFP from or to cells will be studied by using a serum-free culture system with endothelial cells. These cells were selected because they are likely to be exposed to the highest concentrations of AFP and are producers of prostaglandins and related compounds from arachidonic acid, which binds to AFP with a particularly high affinity. These studies may help clarify the physiological role of AFP in the fetus and will generate reagents useful in tumor diagnosis and possibly even therapy.